﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
using System.Linq.Expressions;

namespace Reconciliation.Data
{
    public class Extension
    {
        public static Expression<Func<TElement, bool>> BuildContainsExpression<TElement, TValue>(
        Expression<Func<TElement, TValue>> valueSelector, IEnumerable<TValue> values)
        {
            if (null == valueSelector) { throw new ArgumentNullException("valueSelector"); }
            if (null == values) { throw new ArgumentNullException("values"); }
            ParameterExpression p = valueSelector.Parameters.Single();

            // p => valueSelector(p) == values[0] || valueSelector(p) == ...
            if (!values.Any())
            {
                return e => false;
            }

            var equals = values.Select(
                     value => (Expression)Expression.Equal(valueSelector.Body, Expression.Constant(value, typeof(TValue))));

            var body = equals.Aggregate<Expression>((accumulate, equal) => Expression.Or(accumulate, equal));

            return Expression.Lambda<Func<TElement, bool>>(body, p);
        }
    }
}
